1. Field of the Invention
The present invention generally relates to compressors. More particularly, the present invention relates to a rotary compressor having an improved structure for mounting a compressor pump within a compressor housing.
2. Description of the Related Art
Existing compressors typically include a housing, an electric motor and a compressor pump mounted to the housing, and a shaft rotatably engaged with the electric motor and the compressor pump. The electric motor is commonly powered by an external power source which energizes the stator windings of the motor to turn the motor shaft. In rotary compressors, the shaft drives an eccentric mechanism in the compressor pump to draw, compress and expel a working fluid through a discharge port.
In existing compressors, various methods of mounting a compressor pump within a compressor housing exist. In a rotary compressor such as described in U.S. Pat. No. 4,601,644, a bearing portion of the compressor pump is supported by the compressor housing at several points. The cylindrical compressor housing has holes through its circumference to receive attachment lugs extending from the bearing portion. The attachment lugs extend through the housing holes such that they can be welded directly to the housing from the outside. However, welding the bearing lugs to the housing in this manner may allow debris from the welding process to enter the housing which can damage the compressor. Disadvantageously, these compressors are conducive to leaking through these holes and creating these holes requires additional time and equipment, thereby increasing the cost of the compressor assembly. Additionally, considerable time and effort is expended to align the weld tabs with the housing.
In compressors where the bearing portion or cylinder block of the compressor pump are held in compression against the housing, distortion can occur in the bearing or cylinder block when they are welded to the housing. As the bearing portion or cylinder block, which are commonly made of cast iron or other ductile ferrous materials, are heated during the welding process, the heat is conducted to the shaft support aperture in the bearing portion or the compression chamber of the cylinder block. When exposed to heat, the shaft support aperture and the compression chamber may distort due to stress relaxation of the cast iron, or they may be distorted when they are restricted from expanding due to the compressive spring force of the housing. When restricted, stress may build in the bearing or cylinder block material causing it to permanently deform or yield. Even a small amount of permanent deformation is undesirable as the dimensional tolerances necessary for the proper operation of the rotary compressor are extremely close and are generally on the order of ten thousandth of an inch.
Another disadvantage of using the bearing portion or cylinder block to mount the compressor pump to the housing includes increasing the size of these components to bring a weldable surface in close proximity to the housing. Increasing the size of these members adds weight and cost to the compressor.
What is needed is an improvement over the foregoing.